This paper proposes a novel high speed serial interface in UTMI+ transceiver for USB 2.0 hub repeater operations, so that USB 2.0 hubs can also be supported using the UTMI+ transceivers. The UTMI+ specification is an industry standard which is used to specify an interface to which USB 2.0 ASIC, ASSP, discrete phy, system peripherals, and IP vendors can develop USB 2.0 products. It is the industry standard interface between the USB MAC (host/device/hub) and USB PHY. UTMI+ interface supports 4 levels, namely level 0 to level 3. Each level supports corresponding USB products. However, this specification does not support USB 2.0 hub products, as it cannot comply with the USB 2.0 hub repeater latency requirements, as per table 7–11 of USB 2.0 specification. Hence USB 2.0 hub developers cannot use this industry standard interface for their development, and therefore are forced to use a proprietary/non-standard interface between the USB MAC (hub) and USB PHY (upstream and downstream ports). This issue limits the UTMI+ specification, and thereby the UTMI+ transceiver cannot be reused for USB 2.0 hub products. The aim of this paper is to propose a 5th level (i.e., level 4) to the UTMI+ specification by introducing a novel high speed serial interface (HSI), thereby making the UTMI+ transceiver to support all USB 2.0 products, including USB 2.0 hubs. The proposed interface will fill the gap that prevails in the USB transceiver industry between the USB 2.0 host/device and USB 2.0 hub transceivers. Ultimately, this proposal will make the UTMI+ specification a complete industry standard for all USB 2.0 products, thereby making the UTMI+ transceiver a true reusable component for all USB 2.0 products.
|Keywords:||USB2.0 Hub Repeater Latency Requirements, UTMI+ Specification Limitations, USB 2.0 Specification|
Electrical Design Engineer and Senior Staff, New Product Development Division, Cypress Semiconductor Technology India Pvt. Ltd., Bangalore, Karnataka, India